Ink jet printing has become one of the major imaging technologies used in digital printing applications. The versatility of ink jet has led to an ever increasing number of applications for this technology. In addition to the well established SOHO or desktop market segment, ink jet has now diversified into the business/network, wide format, photo realistic and textile printing applications. These require better image durability in order to provide a print performance as good as existing photographic, lithographic, screen or offset printing technologies. For many of these applications the print must be stable for many years for archiving or the preservation of an image exposed to the environment. The light stability of prints is of particular importance and the improvement of the photo stability of ink jet prints is an important goal.The most important factors in determining the light fastness, of an ink jet print, are the colorant or chromophore, the ink formulation and the ink/media interactions. The photo stability of pigments tends to be superior to that of dyes, however, recent developments in dye chemistry combined with the optimization of ink/media interactions, to protect the chromophore, have produced soluble colorants with light fastness acceptable for many ink jet applications.There has been a rapid development of special media for ink jet applications and in particular for photo realistic and outdoor wide format printing. It has become increasingly clear that the actual environment of the colorant also plays a key role in determining the photo stability of the ink jet print.